Use quotation marks around the exact words of a speaker.
Stanley said, "Can you believe it? I'm a talking horse!"
Introduce a quotation with a word like "said" or "asked" followed by a comma.
I replied, "I wouldn't have believed it if I hadn't heard it."
After the words of the speaker, place end punctuation (or a comma) inside the closing quotation mark.
"I've been talking my whole life," Stanley explained. "Horses have a lot to talk about."